Learning Goal: To understand how to use Hess's law to find the enthalpy of an overall reaction. The change in enthalpy, H, is the heat absorbed or produced during any reaction at constant pressure. Hess's law states that H for an overall reaction is the sum of the H values for the individual reactions. For example, if we wanted to know the enthalpy change for the reaction 3Mn+3O23MnO2 we could calculate it using the enthalpy values for the following individual steps: Step 1: 4Al+3O22Al2O3 Step 2: 3Mn+2Al2O33MnO2+4Al Overall: 3Mn+3O23MnO2 If the enthalpy change is 3352kJ/mol for step 1 and 1792kJ/mol for step 2, then the enthalpy change for the overall reaction is calculated as know the enthalpy change for the reaction 3Mn+3O23MnO2 we could calculate it using the enthalpy values for the following individual steps: Step 1: 4Al+3O22Al2O3 Step 2: 3Mn+2Al2O33MnO2+4Al Overall: 3Mn+3O23MnO2 If the enthalpy change is 3352kJ/mol for step 1 and 1792kJ/mol for step 2, then the enthalpy change for the overall reaction is calculated at: follows: H=3352+1792=1560kJ/mol It is also important to note that the change in enthalpy is a state function, meaning it is independent of path. In other words, the sum of the H values for any set of reactions that produce the desired product from the starting materials gives the same overall H. The equations given in the problem introduction can be added together to give the following reaction: overall:N2O42NO+O2 However, one of them must be reversed. Which one? View Available Hint(s) reaction 1: N2+2O2N2O4 reaction 2: N2+O22NO What is the enthalpy for reaction 1 reversed? reaction 1 reversed: N2O4N2+2O2 Express your answer numerically in kilojoules per mole